This application relates generally to the field of disc drive storage devices, and more particularly, to an apparatus and method for minimizing contact and friction between a disc and a head/slider assembly within a disc drive.
Disc drives are data storage devices that store digital data in magnetic form on a rotating storage medium, such as a disc. Modern disc drives comprise one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a drive motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks typically by an array of transducers (xe2x80x9cheadsxe2x80x9d) each mounted on a slider. Each slider is supported on a flexure attached to an actuator arm which is part of an actuator assembly that moves the head relative to the discs. Each transducer, e.g., a magnetoresistive read/write head, is used to transfer data between a desired track and an external environment. During a write operation, the head writes the data onto the disc track, and during a read operation, the head senses the data previously written on the disc track and transfers the information to a disc drive circuit board in the external environment.
The slider with the head is mounted via flexures at the end of an actuator arm that projects radially outward from an actuator body In the actuator assembly. The actuator body pivots about a bearing assembly mounted on a base plate at a position closely adjacent to the outer extreme of the discs. The head(s) read data and transfer it along the actuator arm to a preamplifier which amplifies the signals coming from the heads.
Typically, the actuator assembly includes a voice coil motor to position the heads with respect to the disc surfaces. The actuator voice coil motor includes a coil mounted to the actuator body opposite the actuator arm and is immersed in the magnetic field of a magnetic circuit comprising one or more permanent magnets and magnetically permeable pole pieces. When controlled direct current (DC) is passed through the coil, an electromagnetic field is set up which interacts with the magnetic field of the magnetic circuit to cause the coil to move in accordance with the well-known Lorentz relationship. As the coil moves, the actuator body and arm pivot about the bearing assembly and the heads move across the disc surfaces.
Historically, the slider support assembly has been loaded or biased by the flexure so that the slider applies a vertical pressure on the disc surface. During the operation of the disc drive, as the drive motor spins, the air pressure between the disc and slider overcomes the vertical downward pressure and causes the slider assembly to fly slightly above the disc surface at a flying height such that there is no friction between the disc surface and the slider. The actuator assembly is typically positioned with the sliders over a portion of the disc surface that contains no sensitive data when the disc drive is not operating, such as the inner most track or margin of the discs. The inner most track is often called the landing zone and typically contains no magnetic recorded information.
However, this approach contains three inherent problems. First, when the disc drive is subjected to shock, the slider will contact the disc and cause nicks and dings crated on the disc surface. Second, with the ultrasmooth finish of the disc surface used today there can be a stiction force generated between the slider and the disc. Stiction is a frictional force which occurs when the slider rests on the disc surface when the disc is not spinning; stiction prevents immediate motion of the disc relative to the slider when the disc first begins to spin and causes a permanent loss of data at the point where the slider touches the disc. Third, the landing zone wastes valuable disc surface space which could otherwise be used to store more data, increasing the value of the disc drive.
One solution to these problems is to provide a loading ramp located beyond the outer diameter of the disc in a disc drive. When the disc drive is not operating, the slider is driven out of the disc area and loaded and parked onto the ramp. In this way, the loading ramp frees up the storage space on the inner diameter of the disc. However, loading ramps can cause the problem of wear particle generation within the disc drive. Loading ramps also may cause the problem of scratching and nicking of the tracks near the outer diameter of the disc surface caused when the slider contacts the disc surface during the loading and unloading of the slider on the ramp. Thus, typically a landing zone is created on the outer diameter of the disc which can waste actually more valuable disc space than the landing zone on the inner diameter of the disc.
Another solution is to load the actuator assembly such that the slider is biased away from the surface of the disc when the disc is at a standstill. In this way, the entire disc surface could be used to store data. However, with the slider biased away from the disc surface, there must be a force to move the slider towards the disc surface and into flying height when the disc is spinning during the operation of the disc drive.
One problematic way to achieve this force is to include a pair of aerodynamic wings on the slider. As the disc rotates, wind generated by the disc rotation pushes against the wings and forces the slider towards the disc until the slider reaches flying height. However, disc drives and disc drive components, including sliders, are becoming smaller and smaller, and it is difficult, if not impossible, to attach a pair of wings large enough to create sufficient force to move the small sized sliders contained in modern disc drives. Additionally, providing aerodynamic wings on the slider interferes with the pitch and roll angle of the slider, which pitch and roll angle is critical for proper function of the disc drive.
Another problematic way to create a force which moves the slider towards the disc during disc drive operation is to include an aerodynamic airfoil formed out of the actuator arm which exerts a negative lift force towards the disc and thereby moves the slider into flying height position. However, the size of the airfoil is limited by the diameter of the actuator arm and therefore may not provide enough force in smaller disc drives. Also, the size and angle of the airfoil is limited by the distance between the slider and the disc surface, and thus, the airfoil may not be large enough to create sufficient downward force in smaller disc drives.
Against this backdrop the present invention has been developed. It is thus desirable to provide an apparatus and method which minimizes the risk of damage to a disc surface caused by contact between a disc and a slider which will be effective in smaller disc drives and which will not interfere with the operation of the disc drive.
A head disc assembly in a disc drive has a base plate and a top cover which encloses a drive motor, a disc supported thereon, and an actuator assembly. The disc spins at a given velocity during operation of the disc drive which causes air flow within the head disc assembly. The actuator assembly has an actuator arm which transfers data to and from the disc.
A flexure has one end connected to the slider and an opposite end connected to the actuator arm. When the disc is stationary, the flexure and the slider are biased away from the disc. One or more airfoils are attached to the flexure and extend from the flexure at an angle relative to the disc so as to interact with the air flow to force the flexure and the attached slider to move toward the disc during operation of the disc drive.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.